The present invention relates to a truck cab roof multipiece fairing assembly wherein the fairing pieces are nested for shipment and attached to the cab roof by a mounting bracket having multiple attachment points for independent nested mounting of the fairing pieces and wherein the fairing pieces are joined through the use of interlocking vertical or horizontal tongue-in-groove joints to cause the exterior surfaces of the fairing pieces to achieve registry and thereby achieve a smooth aerodynamic shape and appearance in the assembled fairing.